Electric hand tool



Fig.

a3 5f; l ,7 l 7,8-, i 0| 5l E.-- Zim 52 /NVEA/I'OR! Feb. 1s, 1936. R, SCHUMANN 1 2,031,133

v EL-ETRI HAND Toor..

Filed J'an. 24, 1953 Fig]- of Fig. `i.

individual sizes of screws.

Patented Feb. i8. i936 application ramener, issasenai ne. stacco In Germany `lanuary 25, 1932 o claims. (ci. 14a-32) This invention relates to an electric hand tool for tightening and loosening screws, in which between the driving element driven` by the motor and the tool serving for engaging the screws a friction clutch is fitted, the driving and driven parts of which are pressed together until they mutually contact against the action of a spring by pressing the tool towards the workpiece.

The object of the invention is to produce a tool of the above mentioned kind in 'which the pressure exerted by the operator for pressing the tool against the workpiece cannot exceed the turning movement necessary for the individual sizes of screws, so that, whilst ensuring against'overturning of the screw, there is a control that the screw is suiciently strongly tightened and it is possible to adjust the turning movement for the ln the known tools of the aforementioned type the turning movement exerted on the portion of the tool engaging the workpiece is merely determined bythe pressure-exerted on the tool which can lead to the overturning 'of the screw to beltightened or to an insumciently strong tightening of the screw.

With clutches the parts of which are adapted to be pressed together against adjustable spring pressure for transmitting the power from the drive to the portion of the tool engaging the workpiece the driving moment is certainly adjustable according to the size of the screws ac-I tually to be tightened but either the'portion of the tool engaging the workpiece must also be continually co-rotated even when the tool is not in engagement with the workpiece, which makes it diiiicult to bring the tool on to the workpiece, or another Aclutch or separate device must be fitted which disconnects the portion of the tool engaging the workpiece from the drive when the tool is removed from the workpiece.

An embodiment of the invention is illustrated by way of example in the accompanying drawing in Whichz Fig. 1 shows in longitudinal section the main portion of the tool according to the invention;

Fig. la is a top plan view of the gearing of the tool.

Fig. 2lshows in elevation a portion of the tool illustrated in Fig. 1.

Fig. 3 is a part cross section on line III-Ill of Fig. 1. V

Fig. 3a. is a part cross-section on line IIIa-IIIa A small high speed electric motor is` mounted in the handle sleeve partly shown in the drawing and composed of a tube preferably made of insu- 4shafts of the toothed wheels 38.

lating material' with a cover (t of elastic insulating material, such as iiuted rubber. The shaft il' i of the motor carries a blade wheel i3. The transwheel 3l. The toothed wheel 3l is keyed on a w spindle l2 which in turn is connected with the clutch half i3 of the friction clutch composed oi the halves (i3 and 33. The clutch half i3 is keyed on the spindle l2 and continually rotates therewith. 52' is a bearing sleeve for the spindle d2 2@ inserted in the head containing the gearing 3d. Discs l5 and it serve as coupling elements of the clutch halves i3 and 33, the disc til having embedded and slightly projecting cork plates ll, whereas the discs it are polished. Grooves are provided one in the outer edge of each of the discs lo and in which grooves a Wedge dit provided in the cylindrical portion of the clutch half 33 surrounding the clutch discs d5 and l5 engages (Fig 3). Grooves are likewise provided 30 one in the inner edge of each of the discs tb and a Wedge t@ provided inthe clutch half t3 er1--I gages therein (Fig. 3o). The discs d@ are rotated by the clutch half "i3 through the intermediary of the wedge l, whereas the discs e5, when ro- 35 tated by the discs llt. rotate -the clutch half 3S through the intermediary of the wedge ed.

An adjustable'stop is provided between the clutch half 33 and the clutch half t3. This stop consists of a nut 9 screwed by means of a ne 40 screw thread on to the spindle d2. Below the nut 49 a supporting ball bearing 5@ is provided against which the clutch half 33 bears when the tool is pressed against the workpiece.. A ball bearing 5i serves as supporting bearing for the .g5

clutch half 43. The clutch is held together by a'eap nut 52. A centering sleeve fvis provided on the clutch half 33 for receiving the tool. An

`aperture is provided in the clutch element 33,

which is hollow and surrounds the mitv t9, to give g@ accessto the nut (Fig. 2). The bores 53 in the nut all serve for inserting a pin for adjusting the nut. iAs the spindle 42 must be held duringvthe adjusting of the nut, a bore 54 is provided in the spindle 42 Vand extended through the clutch 55 with a scale and a mark 56 is provided on the y' clutch half 33. As for adjusting the nut 49 the clutch half 33 must always be rst turned into the position which allows the insertion of the holding pin into the bore 54, scale of the nut is brought in its zero position relative to the mark 56 so that, when adjusting the nut, the mark allows the degree of adjustment to be read on the scale.

The spring 82 bears against the upper edge of the clutch half 33 and presses the clutch halves apart so that the clutch half 43 does not drive the clutch half 33. against the workpiece, the clutch half 33 shifts upwards, compressing the spring 82, so that the clutch elements 45 and 46 or the cork plates 41 on the discs 48 and the discs 46 come into contact. The movement of the clutch half 33 is limited by the nut 49 against which the clutch half 33 bears through the intermediary ofthe supporting ball bearing 50. If the nut is screwed upwards the clutch half 33 can shift further in upward direction so that the clutch .elements 45 and 46 are pressed more strongly together. When the nut is screwed downwards, the clutch half 33 cannot shift so far in upward direction so that the clutch elements are pressed together less strongly. Therefore by sluiting the nut, the intensity of the contact between the clutch halves When the tool is pressed and consequently the turning moment to be transmitted can be regulated as desired so that the tool can be adjusted for different sizes of.

screws.

The motor employed for the tool is reversible so that the tool can be employed for screws with left and right hand screw threads and for tightening and loosening screws.

I claim:

1. An electric hand tool for vtightening and loosening screws, comprising in combination a driving spindle, a stationary clutch half on said spindle, a movable clutch half surrounding said stationary clutch half and axially shiftable relative to said stationary half, a tool carrying sleeve on the lower end of said movable clutch half, said movable clutch half adapted to bear against said stationary clutch half to transmit the movement of said driving spindle to said tool carrying sleeve when the tool is-pressed against the workpiece, and an adjustable stop in the path of movement of said movable clutch half adapted to limit the displacement of said movable clutch half and determine the intensity of contact between said two clutch halves.

2. An electric hand tool as speciiied in claim 1,

- in which the adjustable stop consists of a screw nut on the driving spindle, said nut forming an abutment for the movable clutch half when the tool is pressed against the workpiece.

3. An electric hand tool as specied in claim 1, in which the adjustable stop consists of a screw nut on the driving spindle and the movable clutch half is constructed as a hollow bod'y surrounding said nut and having an aperture giving access 35 to said nut to allow of its adjustment.

' ROBERT SCHMANN. 

